How to make a empty MySQL table? - mysql

What is wrong with the following syntax? This is the code that MySQL work bench made and I can't tell what is wrong with it.
CREATE TABLE `data1`.`table1` ();


You are trying to create a table without columns. That is not possible in MySQL. You need to specify at least one column in order to create table.


You are missing columns, a table need columns
Propper syntax would be:
CREATE TABLE table1(
id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
firstname VARCHAR(30) NOT NULL,
lastname VARCHAR(30) NOT NULL,
email VARCHAR(50),
reg_date TIMESTAMP
);
Read more about this at w3school


A table is a collection of columns and rows. Without columns, it is not a table. 'An empty variable'- would be the best name.
Check the CREATE TABLE syntax here.

Related

How to create sequence for a number that starts at 100 and increment by 5 in MySQL?

I need that the values for a ColumnID, which is a Primary Key, to start at 100 and increment by 5. This condition is asked to be included as a constraint before populating the tables. I already created the tables, I just need to add that constraint. I know I can't use AUTO_INCREMENT because the increase is only by 1. Is there a way to do it in MySQL?

MySQL does not provide any built-in function to create a sequence for a table's rows or columns. But we can generate it via SQL query.
Example:
Let us understand it with the help of the following example. First, we need to create a new table and make sure that there is one column with the AUTO_INCREMENT attribute and that too, as PRIMARY KEY.
Execute the below query to create a table:
CREATE TABLE Insects (
Id INT AUTO_INCREMENT PRIMARY KEY,
Name VARCHAR(30) NOT NULL,
Type VARCHAR(30) NOT NULL,
Origin VARCHAR(30) NOT NULL
);
Then you can alter your column to start from another value:
ALTER TABLE Insects AUTO_INCREMENT=100;
You can check it here.

Adding a column with unique values in AWS Athena

So, I am looking for a way to sequence the rows of my athena table. I have already tried:
ROW_NUMBER() OVER ()
But then this leads to Query exhausted resources at this scale factor error. It has to be a unique value for every row, so yes it doesn't need to be an integer. The method should be performance effective if it can be.

Please provide SHOW CREATE TABLE for the table in question.
If you don't already have an AUTO_INCREMENT column on the table, consider the following.
ALTER TABLE t
ADD COLUMN id INT UNSIGNED AUTO_INCREMENT NOT NULL,
ADD INDEX(id);
If you don't already have a PRIMARY KEY on the table, do this instead:
ALTER TABLE t
ADD COLUMN id INT UNSIGNED AUTO_INCREMENT NOT NULL,
ADD PRIMARY KEY(id);

You can give each row a unique id, uuid, using the uuid() function. Here are the docs:
https://trino.io/docs/current/functions/uuid.html

MySql table columns are automatically adding with existing columns

I have a spring boot application. And I configured my MySql Database table with 3 fields in the DAO Layer. After starting my application this table creating without problem. But after sometime it gets adding 2 more fields with underscore. Please find the below table.
CREATE TABLE `sample` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`contractId` varchar(20) NOT NULL UNIQUE,
`customerName` varchar(50),
PRIMARY KEY (`id`));
After sometime the table is having below fields.
id
contractId
customerName
contract_id
customer_name
Why last two columns are adding without doing anything?
Can anyone please help on this. Thanks

Try to delete these columns :
ALTER TABLE sample
DROP COLUMN contract_id;
DROP COLUMN contract_name;

Existing table add auto increment primary key - sql

I have an existing product table which is already populated with 120 records and I have tried below SQL query:
ALTER TABLE product ADD product_id
INT PRIMARY KEY AUTO_INCREMENT
But it's given me the error:
Error: #1075 - Incorrect table definition; there can be only one auto column and it must be defined as a key

Here is work around
create a simple column with autoincrement
browse the table and again make this newly added column as primary key
You are done !
:) Thanks to Guy who is not in Stackoverflow

Friend
If you try to do this in MSSQL then your script will be this.
suppose your table is below
create table product
(
name varchar(20),
product_type varchar(20)
)
and suppose you entered some record in this table after that you want to add a column that name product_id with auto increment and primary key. Then you use this script that is below
alter table product add product_ID int primary key identity(1,1)
suppose this will be help full for you.

There can only be one auto increment field per table. But, you could have a calculated field based on the auto increment field. Or, you could have an int field where you manage the sequence by front end code or by a trigger. And also you could use a sequence in SQL Server.
CREATE SEQUENCE MySequence START WITH 100;
CREATE TABLE MyTable
(
RealIdentity INT IDENTITY(1,1),
RandomCol NVARCHAR(100),
FakeIdentity INT DEFAULT NEXT VALUE FOR MySequence
);
UPDATE - MySQL Way
I just noticed that your question is taged for MySQL. Above answer is for MS SQL. Here's how you'd do the same in MySQL.
How do I create a sequence in MySQL?
MySQL equivalent of Oracle's SEQUENCE.NEXTVAL

MySQL auto increment based on field?

Is it possible to create auto-increment based on a specific field? For example i have UserId and Status fields, so for each row with same UserId i need to auto-increment its Status, not global.

There is three thing that come to mind when I read your question. One was an auto incrementing field which acts as your ID number. Updating a table with data that has no unique ID number. Searching for fields with the same Userid to Status
Mt First example is of a creating a table and your AUTO_INCREMENTing number ID:
CREATE TABLE tableNameHere
(
UniqueID int NOT NULL AUTO_INCREMENT,
FirstName varchar(255) NOT NULL,
StatusOrYourColumn int(100) NOT NULL,
PRIMARY KEY (UniqueUD)
)
More on auto incrementation.
You may have already built your table and now want to 'add' additional and or modify your fields using ALTER:
ALTER TABLE tableNameHere StatusOrYourColumn INT AUTO_INCREMENT PRIMARY KEY
But be careful, you don't want to overwrite your settings that you have already set.
Another Thing that came to my mind when reading was where you said Status and Userid where the same. You can find these using the WHERE clause like so:
SELECT * FROM tableName WHERE tableName.Userid = anotherTableOrTableName.Status
Using these queries you can update, remake, alter and query your database table.